Eggs, such as those laid and commonly gathered from chickens, include a number of nutritionally valuable components. Typical consumers are familiar with nutrients found in the yolk and egg white (also called the albumen); however, the egg shell and eggshell membrane are also sources of valuable nutrients. The shell contains calcium carbonate, while the membrane is composed of proteins. Upon separation, the shell and the membrane may be used for human food supplements, animal feed supplements, and pharmaceutical purposes. For example, eggshell powder, which is rich in calcium, may be used for both human and animal nutritional supplements. The membrane may be used as a source of collagen, hyaluronic acid, and amino acids. Among other uses, collagen and hyaluronic acid may both be used in the biomedical and cosmetics industries. Moreover, amino acids may be used for animal and human nutrition as well as for cosmetic purposes.
Moreover, the egg shell and eggshell membrane are available as raw product from both processed fertilized and unfertilized eggs that are processed for other purposes. In many cases the eggshell, including the shell and membrane, are treated as waste. Most often, unfertilized eggs are used in foods, while fertilized eggs are hatched to grow chickens. However, in some cases fertilized eggs are not chosen for hatching and enter the market as a food source. As is known in the art, a chick grows from the yolk of an egg, while the egg white remains to provide a food source for the growing chick. Once the eggs have been processed, such as in a food processing or hatching facility, some amount of egg white remains on the eggshells and provides a source of moisture that affects downstream processing.
Although egg shells and eggshell membranes present many valuable uses and are readily available, their value is rarely realized. One primary reason for this is because effective separation of the eggshell and eggshell membrane has historically been met with frustration. One cause for this frustration has been difficulty determining both the optimum moisture content of the eggshell raw product and when in an eggshell membrane separation process drying should occur if necessary. Ascertaining the optimum moisture content is important to an eggshell membrane separation process for a number of reasons. First, eggshell raw product oftentimes contains pathogens from the hatchery facility or other source wherein egg breaking occurs. Oftentimes, pathogens thrive in environments with increased moisture. Accordingly, moisture removal can be beneficial in killing pathogens and preventing same in a finished product.
Next, increased moisture can lead to problems in the separation process. For example, in many processes the egg shell is reduced to a powder or a dust. Excess moisture can mix with the egg shell powder and lead to clogging in the machinery used for separation. On the other hand, too little moisture is also a problem, as the eggshell membrane requires some moisture to stay intact. Accordingly, too little moisture may lead to deterioration of the eggshell membrane during separation. Furthermore, if the moisture content is too low, the membrane may stick to the outer shell, which prevents separation of the two components. Other factors affecting moisture content include temperature and humidity. Accordingly, there exists a need in the art for a process to separate an egg shell from an eggshell membrane that includes the appropriate moisture level of the eggshell raw product. Moreover, the process should optimize the stage at which moisture level adjustment occurs.
Some previous methods of eggshell processing and membrane separation are known. For example, U.S. Pat. No. 6,649,203 to Thoroski discloses methods and an apparatus for processing eggshells. The methods disclosed therein include embodiments wherein egg shell and membrane are both processed together and separated for individual purposes. In the method to separate the shell and membrane, the raw product is initially centrifuged to remove residual liquid. The raw product is then washed and centrifuged to remove the wash liquid. Next, the eggshells are dried via heat and tumbled to bring about separation of the shell and membrane. Specifically, the eggshells are heated to 88 degrees Celsius for two minutes to reduce the moisture content to 1-3%. The heat from the drying process breaks protein attachments connecting the shell and membrane and, therefore, effects separation of same. Tumbling action accomplishes further separation.
The products are separated a first time by sieving, which removes large pieces of membrane and leaves behind small pieces of membrane and the shell pieces. The remaining small membrane and shell pieces are then delivered to a hammer mill for further size reduction. The shell and membrane pieces are then separated based on their relative densities, with the membrane pieces removed by a pneumatic removal system while the shell pieces collect in bottom of the hammer mill housing. The above-described process is inefficient in that it requires multiple drying steps before detaching the eggshell membrane from the eggshell. Additionally, steps beyond drying, namely a washing step, must be used to effectively remove pathogens. In an alternate embodiment, the eggshell raw product may be centrifuged, washed, and dried as described above. The eggshells are then processed and separated in the hammer mill without further processing.
U.S. Pat. No. 6,649,203 further describes processes wherein egg shell and eggshell membrane may be processed together for future uses. In one such process, the egg shell and membrane are placed in a rotary drum dryer to remove excess water and pasteurize the eggshells. After drying, the eggshells are processed in a hammer mill, which reduces the eggshells to a powder. The powder includes both the egg shell and the eggshell membrane and may be used for chicken feed. The process fails to separate the shell and membrane to be used for their individual value added purposes.
Processes such as those disclosed in the above-described U.S. Pat. No. 6,649,203 which include a hammer mill are not well suited for separating egg shell and membrane. As is known in the art, a hammer mill includes a number of hammers which are mounted onto a rotating shaft or drum. As the shaft or drum rotates, the hammers collide with material that has been fed into the hammer mill. In addition to the hard outer shell, a hammer mill will also reduce the eggshell membrane to smaller pieces. Accordingly, separation is difficult or impossible. Therefore, membrane yield is less when using a hammer mill than when using other types of grinders, such as ultrasonic grinders or devices that employ airflow.
For example, in a process described in United States Patent Application Publication No. 2011/0272502 to New, which is hereby incorporated by reference, a system and process for separating eggshell membranes utilizing airflow is disclosed. The system pushes the airflow through a venturi to pulverize the unprocessed eggshells, which separates the outer shell from the membrane. Flow of the air through the venturi creates pressure changes, which may create one or more shockwaves, resulting in pulverization of the brittle outer shell of the eggshell. The reference anticipates that the membranes will be left intact. Accordingly, the pulverized outer shell and membranes may be separated by means such as a cyclone separator or shaker screen with the appropriate mesh size. However, the system and process disclosed in United States Patent Application Publication No. 2011/0272502 presents difficulties that have not previously been overcome. Namely, the machinery, especially the devices creating the airflow and through which the airflow passes, often clogs with material. In addition, the airflow can also pulverize the membrane, preventing effective separation of the outer shell and the membrane.
Accordingly, there is a need in the art for an improved process for separating eggshells and eggshell membranes so that the value of each may be realized. Such a process should prevent both the machinery from clogging with material and the membrane from being pulverized. Such a process should adjust the starting material to the optimum moisture content, which in some embodiments may be accomplished by drying the eggshell raw product for a particular time and in a particular sequence. Said process will preferably allow for commercial scale processing of eggshell raw product and be capable of continuous operation. Moreover, an improved process will preferably kill pathogens present on the eggshell raw product.